DropDMG lets you split large disk images into multiple pieces, to keep the size
of each file below a set limit. This can be useful for transferring large files
over the Internet or burning them to disc. The filenames of the pieces will end
with .dmg, .002.dmgpart, .003.dmgpart, etc.

To access the contents of a segmented disk image, make sure the .dmg file
and all the .dmgpart files are in the same folder. (If you had burned the
pieces to disc you would need to copy them all back to the same folder on a hard
drive.) Then double-click the .dmg file or use DropDMG’s Mount Image…
command.

To split an existing disk image into smaller pieces, set the segment size and
then use the Convert Image/Archive… command.

To join multiple segments into a single disk image file, make sure that all the
segments are in the same folder, uncheck Limit segments to ___ MB, and then
use the Convert Image/Archive… command.

Segmented ZIP Archives

DropDMG can create segmented ZIP archives (e.g. .z01, .z02, .zip).
Such archives cannot be expanded by Mac OS X’s built-in Archive Utility, but
there are free third-party expansion utilities such as The Unarchiver.

Segment Sizes

Sizes are specified in megabytes (base 10). The Sizes pop-down menu lets you
enter common segment sizes for CDs, DVDs, and Blu-ray discs. The sizes are
chosen so that a segment of that size can be burned to the disc as a file. The
actual disc capacities may vary slightly, as will the sizes of the segments
produced by the disk imaging engine.